1. Field of the Invention
The present invention relates to an apparatus for depositing a material on an internal surface of a metal pipe, which is also known as weld-mounting, and particularly to a weld-mounting apparatus provided with a monitor device for monitoring the state of the weld-mounting.
2. Description of the Related Art
Steel pipes high in corrosion resistance and excellent in elosion resistance are required for petroleum production, petroleum transportation, etc. Therefore, in most cases, high-alloy powder is deposited or weld-mounted to the inner surface of the low-alloy steel pipes before the steel pipes are used.
These types of steel pipes have lengths ranging from 2 to 12 m. Consequently, it is difficult for an operator to confirm and monitor the weld-mounting of an inner surface of each pipe by a weld-mounting apparatus. Therefore, after weld-mounting, the pipes are inspected for defects by eye observation using an endoscope to evaluate products. In the inspection, it is very difficult to accurately specify positions of weld-mounting defects and repair the defects. As a result, products having detected defects are regarded as inferior products. This results in an increase in the cost of production and delay in the time of delivery.
It is an object of the present invention to provide a metal pipe inner surface weld-mounting apparatus having a monitoring device capable of finding the occurrence of failure such as abnormality of weld-mounting beads, abnormality of arc light, or the like, in a weld-mounting operation and taking an early countermeasure against the failure to thereby prevent rejected products from being produced.
According to a first aspect of the present invention, an apparatus for weld-mounting a metal pipe internal surface having a monitoring device comprises;
a horizontally extending arm having a supported base end and a leading end;
a torch attached to a portion of said arm near said leading end of the arm, weld-mounting being performed on an internal surface of a metal pipe supported and rotatable about a horizontally extending axis while at least one of the metal pipe and the horizontal torch is moveable in a direction along the horizontal axis;
a mirror attached at the leading end of the arm;
a camera positioned in spaced apart relation to the mirror for picking up an image of weld-mounting beads in a vicinity of arc light of the horizontal torch through the mirror; and
a monitoring device for monitoring a condition of the weld-mounting.
According to a second aspect of the present invention, in the apparatus of the first aspect, the monitoring device is a monitor which displays an output video signal of the camera as an image.
According to the second aspect, an image of the weld-mounting beads in the neighborhood of the arc light is picked up by the camera as a reflected image by the mirror, and displayed by the monitor. Hence, abnormality of the weld-mounting beads can be found immediately by observation with the monitor in a weld-mounting operation, so that a necessary countermeasure can be taken.
According to a third aspect of the present invention, in the apparatus of the second aspect, the camera picks up an image of the arc light, on one and the same screen, as well as the image of the weld-mounting beads.
According to the third aspect, the reflected image of the weld-mounting beads and an image of the arc light are displayed on one and the same screen by the monitor. Hence, abnormality of the weld-mounting beads and abnormality of the arc light can be found immediately by observation with the monitor in a weld-mounting operation, so that a necessary countermeasure can be taken.
According to a fourth aspect of the present invention, in the apparatus of the first aspect, the monitoring device is an image processing unit for making a judgment, on the basis of an output video signal of the camera, as to whether weld-mounting is good or not.
According to the fourth aspect, the image of the weld-mounting beads in the neighborhood of the arc light is picked up by the camera as an image reflected by the mirror so as to be used for making a judgment as to whether weld-mounting is good or not by the image processing unit on the basis of the output video signal of the camera. Hence, abnormality of weld-mounting can be found immediately on the basis of the judgment output of the image processing unit in a weld-mounting operation, so that a necessary countermeasure can be taken.
According to a fifth aspect of the present invention, in the apparatus of the fourth aspect, the camera picks up an image of the arc light, on one and the same screen, as well as the image of the weld-mounting beads.
According to the fifth aspect, the image processing unit makes a judgment as to whether weld-mounting is good or not on the basis of the video signal of the reflected image of the weld-mounting beads and the video signal of the arc light. Hence, abnormality of the weld-mounting beads and abnormality of the arc light can be found immediately on the basis of the judgment output of the image processing unit in a weld-mounting operation, so that a necessary countermeasure can be taken.
In the present invention, a suitable filter can be used for the camera. According to a sixth aspect of the present invention, in the apparatus of the first to fifth aspects, if a filter for attenuating the arc light relatively greatly compared with light incident on the camera from the weld-mounting beads is provided between the mirror and the camera, the difference in brightness between the image of the weld-mounting beads and the image of the arc light formed on an image pick-up surface portion of the camera can be reduced so that the two images can be picked up as sharp images desirably.
In the present invention, any special cooling unit need not be additionally provided in the metal-pipe. According to the seventh aspect of the present invention, in the apparatus of the first to sixth aspects, if a cooling unit for circulating a cooling fluid is provided on an outer circumferential portion of the metal pipe, the quantity of bending of the metal pipe due to the influence of heat can be suppressed even in the case where the quantity of heat inputted by the arc light is large. Hence, the image reflected from the mirror can be prevented from being displaced out of the screen because of the change of the distance between the mirror and the inner surface of the metal pipe. Hence, this is desirable because fine adjustment of the upper and lower positions of the camera and the angle of the optical axis need not be repeated.
In the present invention, any special cooling unit need not be provided on the mirror. According to the eighth aspect of the present invention, in the apparatus of the first to seventh aspects, if a mirror cooling unit for circulating a gas for cooling a light-receiving surface of the mirror is provided on the light-receiving surface side of the mirror, the light-receiving surface of the mirror can be prevented from being melted and damaged by heat radiated from the high-temperature arc light or the high-temperature weld-mounting metal portion. Hence, the reflected image of the weld-mounting beads can be picked up, as an always sharp image, by the camera desirably.
The present invention can be applied to an apparatus for weld-mounting an inner surface of each of various types of metal pipes. According to the ninth aspect of the present invention, in the apparatus of the first to eighth aspects, if the metal pipe is a steel pipe, there can be obtained a monitor-containing steel pipe inner surface weld-mounting apparatus which is particularly suitable and greatly effective for weld-mounting on a steel pipe for petroleum production, petroleum transportation, etc. requiring weld-mounting on a large deal of long steel pipe.